JP7461080B2 - Lithium secondary batteries and anode-free batteries - Google Patents

Description

The present invention relates to a lithium secondary battery and an anode-free battery.

In recent years, technology for converting natural energy such as sunlight or wind power into electrical energy has been attracting attention. Along with this, various secondary batteries have been developed as power storage devices that are highly safe and can store a large amount of electrical energy.

Among them, secondary batteries that charge and discharge by moving metal ions between the positive and negative electrodes are known to exhibit high voltage and high energy density, and are typically lithium ion secondary batteries. It has been known. A typical lithium-ion secondary battery is one in which active materials capable of holding lithium are introduced into the positive and negative electrodes, and charging and discharging are performed by transferring lithium ions between the positive and negative active materials. Can be mentioned. Furthermore, as a secondary battery that does not use an active material in the negative electrode, a lithium metal secondary battery that retains lithium by depositing lithium metal on the surface of the negative electrode has been developed.

For example, Patent Document 1 discloses a high-energy density, high-power lithium metal anode secondary battery having a volumetric energy density exceeding 1000 Wh/L and/or a mass energy density exceeding 350 Wh/kg when discharged at a rate of at least 1 C at room temperature. Patent Document 1 discloses the use of an ultra-thin lithium metal anode to realize such a lithium metal anode secondary battery.

Patent Document 2 also discloses a lithium secondary battery including a positive electrode, a negative electrode, a separator and an electrolyte interposed between them, in which metal particles are formed on a negative electrode current collector of the negative electrode, and are transferred from the positive electrode by charging to form lithium metal on the negative electrode current collector in the negative electrode. Patent Document 2 discloses that such a lithium secondary battery can provide a lithium secondary battery with improved performance and life by solving problems caused by the reactivity of lithium metal and problems that occur during the assembly process.

Special table 2019-517722 publication Special table 2019-537226 publication

However, after the inventors conducted a detailed study of conventional batteries, including those described in the above patent documents, they found that at least one of the energy density, capacity, and cycle characteristics was insufficient.

For example, typical secondary batteries that charge and discharge by the exchange of metal ions between positive and negative active materials have insufficient energy density and capacity. In addition, conventional anode-free lithium secondary batteries that retain lithium by depositing lithium metal on the surface of the negative electrode are prone to the formation of dendritic lithium metal on the surface of the negative electrode through repeated charging and discharging, which makes them prone to short circuits and capacity loss. As a result, the cycle characteristics are insufficient.

In addition, in anode-free lithium secondary batteries, a method has been developed in which a large physical pressure is applied to the battery to keep the interface between the negative electrode and the separator at high pressure in order to suppress the discrete growth of lithium metal during precipitation. However, the application of such high pressure requires a large mechanical mechanism, which increases the weight and volume of the entire battery and reduces its energy density.

The present invention has been made in consideration of the above problems, and aims to provide a lithium secondary battery and an anode-free battery that have high energy density and capacity and excellent cycle characteristics.

A lithium secondary battery according to an embodiment of the present invention includes a positive electrode current collector, a negative electrode having no negative electrode active material, a separator disposed between the positive electrode current collector and the negative electrode, and the positive electrode collector. A positive electrode having a positive electrode active material disposed between the electric body and the separator, and an electrolyte, and a layer containing an anion-adsorbing conductive polymer between the positive electrode current collector and the separator. include.

The above-mentioned lithium secondary battery is equipped with a negative electrode that does not have a negative electrode active material, so that lithium metal is deposited on the surface of the negative electrode, and charging and discharging is performed by electrolytically dissolving the deposited lithium metal. High density.

Furthermore, for the following reasons, the lithium secondary battery has excellent cycle characteristics and higher energy density and capacity. In conventional anode-free type lithium secondary batteries, there is a tendency to increase the lithium ion concentration in the electrolyte in order to improve cycle characteristics, but the lithium ions in the electrolyte are not sufficient for the precipitation of lithium metal. Since it is not consumed, such a high concentration of lithium ions in the electrolyte is disadvantageous from the point of view of increasing energy density. On the other hand, in the lithium secondary battery, during charging, the anion-adsorbing conductive polymer adsorbs anions contained in the electrolyte, so not only lithium ions originating from the positive electrode but also anions in the electrolyte are absorbed. By consuming lithium ions, which are counter ions, lithium metal can be deposited on the negative electrode, and even when an electrolytic solution containing a high concentration of lithium ions is used, the energy density and capacity can be increased. Furthermore, the reaction in which the anion-adsorbing conductive polymer adsorbs anions contained in the electrolyte is more likely to occur than the reaction in which lithium ions are desorbed from the positive electrode. , the reaction rate of lithium metal precipitation on the negative electrode becomes slower. As a result, in the lithium secondary battery, the growth of dendrite-like lithium metal on the negative electrode is suppressed, resulting in excellent cycle characteristics.

A lithium secondary battery according to one embodiment of the present invention comprises a positive electrode current collector, a negative electrode having no negative electrode active material, a solid electrolyte disposed between the positive electrode current collector and the negative electrode, and a positive electrode having a positive electrode active material disposed between the positive electrode current collector and the solid electrolyte, and includes a layer containing an anion-adsorbing conductive polymer between the positive electrode current collector and the solid electrolyte.

In a lithium secondary battery having a solid electrolyte as described above, anions contained in the solid electrolyte are adsorbed to the anion-adsorbing conductive polymer, so that lithium ions contained in the solid electrolyte are absorbed into the negative electrode. Since it is deposited on top, it does not need to contain an electrolyte. According to such an aspect, since the lithium secondary battery can be a solid battery, a lithium secondary battery with even higher safety can be obtained.

In the lithium secondary battery, a polymer layer containing the anion-adsorbing conductive polymer may be disposed between the positive electrode current collector and the positive electrode. According to such an embodiment, since the positive electrode current collector and the polymer layer are in direct contact with each other, anions are more likely to be adsorbed in the anion-adsorbing conductive polymer, and the lithium secondary battery has better cycle characteristics. will improve.

In the lithium secondary battery, a polymer layer containing the anion-adsorbing conductive polymer may be disposed on a surface of the positive electrode opposite to the positive electrode current collector.

In the lithium secondary battery, the anion-adsorbing conductive polymer may be included in the positive electrode.

The content of the anion-adsorbing conductive polymer in the lithium secondary battery is preferably 1% or more in terms of capacity ratio to the total capacity of the positive electrode active material and the anion-adsorbing conductive polymer. It is 15% or less. According to such an embodiment, a better balance between energy density, capacity, and cycle characteristics can be achieved.

The lithium secondary battery may be a lithium secondary battery in which lithium metal is deposited on the surface of a negative electrode, and charging and discharging are performed by dissolving the deposited lithium. According to such an embodiment, the energy density becomes even higher.

The negative electrode is preferably an electrode made of at least one selected from the group consisting of Cu, Ni, Ti, Fe, and other metals that do not react with Li, and alloys thereof, and stainless steel (SUS). According to such an embodiment, highly flammable lithium metal is not required during production, resulting in even greater safety and productivity. In addition, such a negative electrode is stable, and therefore the cycle characteristics of the secondary battery are further improved.

Preferably, in the lithium secondary battery, no lithium foil is formed on the surface of the negative electrode before initial charging. According to such an embodiment, since it is not necessary to use highly flammable lithium metal during manufacturing, safety and productivity are further improved.

The lithium secondary battery preferably has an energy density of 350 Wh/kg or more.

An anode-free battery according to one embodiment of the present invention comprises a positive electrode current collector, a negative electrode, a separator disposed between the positive electrode current collector and the negative electrode, a positive electrode having a positive electrode active material disposed between the positive electrode current collector and the separator, and an electrolyte, and includes a layer containing an anion-adsorbing conductive polymer between the positive electrode current collector and the separator.

Since the battery is an anode-free battery, it has a high energy density. In addition, the anode-free battery has excellent cycle characteristics and a higher energy density and capacity for the following reasons. In conventional anode-free batteries, the concentration of electrolyte in the electrolyte solution tends to be increased in order to improve cycle characteristics, but since the metal ions in the electrolyte solution are not consumed for metal precipitation, such a high concentration of electrolyte in the electrolyte solution is disadvantageous in terms of increasing energy density. On the other hand, in the anode-free battery, the anion-adsorbing conductive polymer adsorbs anions contained in the electrolyte solution during charging, so that metal can be precipitated on the negative electrode by consuming not only metal ions derived from the positive electrode but also metal ions that are counterions of the anions in the electrolyte solution, and the energy density and capacity can be increased even when an electrolyte solution containing a high concentration of metal ions is used. Furthermore, since the reaction in which the anion-adsorbing conductive polymer adsorbs anions contained in the electrolyte solution occurs more easily than the reaction in which metal ions are released from the positive electrode, the reaction rate of the metal deposition reaction on the negative electrode is slow in the early stage of charging in the anode-free battery. As a result, in the anode-free battery, the growth of dendritic metal on the negative electrode is suppressed, resulting in excellent cycle characteristics.

According to the present invention, it is possible to provide a lithium secondary battery and an anode-free battery that have high energy density and capacity and excellent cycle characteristics.

FIG. 1 is a schematic cross-sectional view of a lithium secondary battery according to the first embodiment. FIG. 1 is a schematic cross-sectional view of a lithium secondary battery according to a first embodiment of the present invention; FIG. 2 is a schematic cross-sectional view of a lithium secondary battery according to a second embodiment of the present invention. FIG. 3 is a schematic cross-sectional view of a lithium secondary battery according to a third embodiment. FIG. 3 is a schematic cross-sectional view of a lithium secondary battery according to a fourth embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention (hereinafter referred to as "this embodiment") will be described in detail below, with reference to the drawings as necessary. In addition, in the drawings, the same elements are given the same reference numerals, and overlapping explanations will be omitted. In addition, the positional relationships such as top, bottom, left, and right are based on the positional relationships shown in the drawings unless otherwise specified. Furthermore, the dimensional ratios in the drawings are not limited to the illustrated ratios.

[First embodiment]
(Lithium secondary battery)
FIG. 1 is a schematic cross-sectional view of a lithium secondary battery according to the first embodiment. As shown in FIG. 1, the lithium secondary battery 100 of the first embodiment includes a positive electrode 110, a negative electrode 140 having no negative electrode active material, and a separator 130 disposed between the positive electrode 110 and the negative electrode 140. , a polymer layer 120 disposed between the positive electrode 110 and the separator 130, and an electrolytic solution not shown in FIG. The positive electrode current collector 150 is disposed on the opposite side of the surface of the positive electrode 110 that faces the polymer layer 120.

(Negative electrode)
The negative electrode 140 does not have a negative electrode active material. In a lithium secondary battery equipped with a negative electrode having a negative electrode active material, it is difficult to increase the energy density due to the presence of the negative electrode active material. On the other hand, since the lithium secondary battery 100 of this embodiment includes the negative electrode 140 without a negative electrode active material, such a problem does not occur. That is, the lithium secondary battery 100 of this embodiment has high energy density because charging and discharging are performed by depositing lithium metal on the negative electrode 140 and electrolytically dissolving the deposited lithium metal.

In this embodiment, unless otherwise specified, "lithium metal is deposited on the negative electrode" refers to the surface of the negative electrode and the solid electrolyte interface layer (SEI layer) formed on the surface of the negative electrode, which will be described later. This means that lithium metal is deposited on at least one location on the surface. Therefore, in the lithium secondary battery 100, lithium metal may be deposited, for example, on the surface of the negative electrode 140 (at the interface between the negative electrode 140 and the separator 130).

In this specification, unless otherwise specified, "negative electrode active material" means a material for holding lithium ions or lithium metal in the negative electrode 140, It may also be referred to as a host substance. Such a retention mechanism is not particularly limited, but includes, for example, intercalation, alloying, and occlusion of metal clusters, and is typically intercalation.

Examples of such negative electrode active materials include, but are not limited to, carbon-based materials, metal oxides, metals that alloy with lithium, and alloys containing such metals. Examples of the carbon-based materials include, but are not limited to, graphene, graphite, hard carbon, mesoporous carbon, carbon nanotubes, and carbon nanohorns. Examples of the metal oxides include, but are not limited to, titanium oxide compounds, tin oxide compounds, and cobalt oxide compounds. Examples of the metals that alloy with lithium include silicon, germanium, tin, lead, aluminum, and gallium.

The negative electrode 140 is not particularly limited as long as it does not have a negative electrode active material and can be used as a current collector, but examples thereof include at least one selected from the group consisting of Cu, Ni, Ti, Fe, and other metals that do not react with Li, and alloys thereof, as well as stainless steel (SUS). When SUS is used for the negative electrode 140, various types of SUS that have been known in the art can be used. The above-mentioned negative electrode materials are used alone or in combination of two or more types. In this specification, the term "metal that does not react with Li" refers to a metal that does not react with lithium ions or lithium metal to form an alloy under the operating conditions of a lithium secondary battery.

The negative electrode 140 is preferably an electrode that does not contain lithium. According to such an embodiment, since there is no need to use highly flammable lithium metal during production, the lithium secondary battery 100 is even safer and more productive. From the same viewpoint and from the viewpoint of improving the stability of the negative electrode 140, the negative electrode 140 is more preferably made of at least one selected from the group consisting of Cu, Ni, and alloys thereof, and stainless steel (SUS). From the same viewpoint, the negative electrode 140 is more preferably made of Cu, Ni, or an alloy thereof, and is particularly preferably made of Cu or Ni.

As used herein, "the negative electrode does not contain a negative electrode active material" means that the content of the negative electrode active material in the negative electrode is 10% by mass or less based on the entire negative electrode. The content of the negative electrode active material in the negative electrode is preferably 5.0% by mass or less, may be 1.0% by mass or less, and may be 0.1% by mass or less, based on the entire negative electrode. , 0.0% by mass or less. Note that the fact that the lithium secondary battery 100 includes a negative electrode without a negative electrode active material means that the lithium secondary battery 100 is an anode-free secondary battery, a zero-anode secondary battery, or an anode-free secondary battery in the commonly used sense. This means that it is a non-rechargeable secondary battery.

The capacity of the negative electrode 140 is sufficiently small compared to the capacity of the positive electrode 110, and may be, for example, 20% or less, 15% or less, 10% or less, or 5% or less. Therefore, the negative electrode 140 can also be said to be a negative electrode current collector. The capacities of the positive electrode 110 and the negative electrode 140 can be measured by a conventional method.

The average thickness of the negative electrode 140 is preferably 4 μm or more and 20 μm or less, more preferably 5 μm or more and 18 μm or less, and even more preferably 6 μm or more and 15 μm or less. According to such an embodiment, the volume occupied by the negative electrode 140 in the lithium secondary battery 100 is reduced, and the energy density of the lithium secondary battery 100 is further improved.

(Positive electrode)
The positive electrode 110 is not particularly limited as long as it has a positive electrode active material and is generally used in lithium secondary batteries, but a known material can be appropriately selected depending on the application of the lithium secondary battery. Since the positive electrode 110 has a positive electrode active material, it has high stability and output voltage.

In this specification, "positive electrode active material" means a material for retaining lithium element (typically, lithium ions) in the positive electrode 110, and may be referred to as a host material for the lithium element (typically, lithium ions).

Such positive electrode active materials include, but are not particularly limited to, metal oxides and metal phosphates. Examples of the metal oxide include, but are not particularly limited to, cobalt oxide compounds, manganese oxide compounds, and nickel oxide compounds. The metal phosphates are not particularly limited, but include, for example, iron phosphate compounds and cobalt phosphate compounds. Typical positive electrode active materials include LiCoO ₂ , _LiNix Co _y Mn _z O (x+y+z=1), _LiNix Mn _y O (x+y=1), LiNiO ₂ , LiMn ₂ O ₄ , LiFePO, LiCoPO, LiFeOF, Examples include LiNiOF and _TiS2 . The above positive electrode active materials may be used alone or in combination of two or more.

The positive electrode 110 may contain components other than the positive electrode active material described above. Such components include, but are not particularly limited to, known conductive aids, binders, solid polymer electrolytes, and inorganic solid electrolytes.

The conductive additive in the positive electrode 110 is not particularly limited, but examples thereof include carbon black, single-walled carbon nanotubes (SWCNT), multi-walled carbon nanotubes (MWCNT), carbon nanofibers (CF), and acetylene black. The binder is not particularly limited, but examples thereof include polyvinylidene fluoride, polytetrafluoroethylene, styrene butadiene rubber, acrylic resin, and polyimide resin.

The content of the positive electrode active material in the positive electrode 110 may be, for example, 50% by mass or more and 100% by mass or less with respect to the entire positive electrode 110. The content of the conductive support agent may be, for example, 0.5% by mass or less than 30% by mass with respect to the entire positive electrode 110. The content of the binder may be, for example, 0.5% by mass and 30% by mass or less with respect to the entire positive electrode 110. The total content of the solid polymer electrolyte and the inorganic solid electrolyte may be, for example, 0.5% by mass and 30% by mass or less with respect to the entire positive electrode 110.

(Positive electrode current collector)
A positive electrode current collector 150 is arranged on one side of the positive electrode 110. The positive electrode current collector 150 is not particularly limited as long as it is a conductor that does not react with lithium ions in the battery. An example of such a positive electrode current collector is aluminum.

The average thickness of the positive electrode collector 150 is preferably 4 μm or more and 20 μm or less, more preferably 5 μm or more and 18 μm or less, and even more preferably 6 μm or more and 15 μm or less. According to such an embodiment, the volume occupied by the positive electrode collector 150 in the lithium secondary battery 100 is reduced, and the energy density of the lithium secondary battery 100 is further improved.

(Separator)
The separator 130 is a member that prevents short-circuiting of the battery by separating the positive electrode 110 and the negative electrode 140 while ensuring ionic conductivity of lithium ions that serve as charge carriers between the positive electrode 110 and the negative electrode 140. It is made of a material that has no electronic conductivity and does not react with lithium ions. Furthermore, the separator 130 also plays a role of holding the electrolyte. The separator 130 is not limited as long as it plays the above-mentioned role, but is made of, for example, a porous polyethylene (PE) film, a polypropylene (PP) film, or a laminated structure thereof.

Separator 130 may be covered with a separator coating layer. The separator coating layer may cover both sides of the separator 130, or may cover only one side. The separator coating layer is not particularly limited as long as it is a material that has ion conductivity and does not react with lithium ions, but it is preferably a material that can firmly adhere the separator 130 and a layer adjacent to the separator 130. . Examples of such a separator coating layer include, but are not limited to, polyvinylidene fluoride (PVDF), a mixture of styrene butadiene rubber and carboxymethyl cellulose (SBR-CMC), polyacrylic acid (PAA), and lithium polyacrylate. (Li-PAA), polyimide (PI), polyamideimide (PAI), and those containing binders such as aramid. For the separator coating layer, inorganic particles such as silica, alumina, titania, zirconia, magnesium oxide, magnesium hydroxide, lithium nitrate, etc. may be added to the binder. Note that the separator 130 includes a separator having a separator coating layer.

The average thickness of the separator 130 is preferably 30 μm or less, more preferably 25 μm or less, and still more preferably 20 μm or less. According to such an embodiment, the volume occupied by the separator 130 in the lithium secondary battery 100 is reduced, so that the energy density of the lithium secondary battery 100 is further improved. Further, the average thickness of the separator 130 is preferably 5 μm or more, more preferably 7 μm or more, and still more preferably 10 μm or more. According to such an embodiment, the positive electrode 110 and the negative electrode 140 can be isolated more reliably, and short-circuiting of the battery can be further prevented.

(Polymer Layer)
The polymer layer 120 is a layer containing an anion-adsorbing conductive polymer, and is preferably a layer made of an anion-adsorbing conductive polymer. The polymer layer 120 is disposed between the separator 130 and the positive electrode 110, and may be formed on the separator 130 side or on the positive electrode 110 side. The lithium secondary battery 100 is preferably configured so that the polymer layer 120 contacts the positive electrode 110. When the polymer layer 120 is not configured to contact the positive electrode 110, the lithium secondary battery may be pressured in the thickness direction of the battery so that the polymer layer 120 contacts the positive electrode 110 during use.

In this specification, the term "anion-adsorbing conductive polymer" refers to a polymer that adsorbs or can adsorb anions during charging of the battery, has conductivity, or exhibits conductivity due to the adsorption of the anions. Since the polymer layer 120 has such an anion-adsorbing conductive polymer, during charging of the lithium secondary battery 100, it adsorbs anions contained in the electrolyte and supplies electrons to the negative electrode 140 via the positive electrode 110 and the positive electrode current collector 150. Here, in order to maintain electrical neutrality in the electrolyte, the lithium ions, which are counterions of the adsorbed anions, are reduced on the negative electrode 140 as a whole in the lithium secondary battery 100, and lithium metal is precipitated on the negative electrode. Such precipitation of lithium metal on the negative electrode due to the adsorption of anions is more likely to occur (occurs under low voltage conditions) than precipitation of lithium metal on the negative electrode due to the desorption of lithium ions from the positive electrode active material, so in the lithium secondary battery 100, the reaction rate of the lithium metal precipitation reaction on the negative electrode is slow in the early stage of charging. As a result, the growth of dendritic lithium metal on the negative electrode is suppressed, and the lithium secondary battery 100 has excellent cycle characteristics. However, the factors that give the lithium secondary battery 100 excellent cycle characteristics are not limited to the above.

In addition, as mentioned above, during charging, especially in the initial stage of charging, the lithium secondary battery 100 consumes lithium ions in the electrolyte and deposits lithium metal on the negative electrode, so the energy density and capacity decrease for the following reasons. expensive. In other words, in conventional anode-free lithium secondary batteries, there is a tendency to increase the lithium ion concentration in the electrolyte in order to improve cycle characteristics, but lithium ions in the electrolyte tend to increase due to the precipitation of lithium metal. Such high concentration of lithium ions is disadvantageous from the viewpoint of increasing energy density. On the other hand, in the lithium secondary battery 100 in which lithium ions in the electrolyte are consumed and lithium metal is deposited on the negative electrode, the lithium ions in the electrolyte can be used as a lithium source. The high concentration of lithium ions is not disadvantageous from the viewpoint of energy density, and it is possible to achieve both excellent cycle characteristics and high energy density and capacity. However, the factors that enable the lithium secondary battery 100 to achieve both excellent cycle characteristics and high energy density and capacity are not limited to the above.

Note that "early charging" refers to the charging stage when the battery's state of charge (SOC) is low, for example, when the charge rate is 40% or less, 25% or less, or 10% or less. However, the above specific values also depend on the content of the anion-adsorbing conductive polymer. The battery's charge rate can be estimated by measuring the open-circuit voltage of the battery.

The anion-adsorbing conductive polymer is not particularly limited as long as it is a polymer that adsorbs or can adsorb anions during battery charging, has electrical conductivity, or exhibits electrical conductivity by adsorbing the anions. From the viewpoint of further improving the cycle characteristics of the lithium secondary battery 100, the anion-adsorbing conductive polymer is capable of anion doping, i.e., adsorbing anions, at a potential of preferably 3.0 V or less, more preferably 2.5 V or less, and even more preferably 2.0 V or less relative to the lithium counter electrode.

Examples of the anion-adsorbing conductive polymer include polymers having a conjugated system in the polymer main chain. When such a polymer is applied with a predetermined potential in an electrolytic solution, anions in the electrolytic solution are doped and the polymer exhibits conductivity. Express. Non-limiting examples of anion adsorbing conductive polymers include polyacetylene, polyaniline, polypyrrole, polythiophene, polyethylene dioxythiophene, poly p-phenylene, polyfluorene, poly p-phenylene vinylene, and polythienylene vinylene; These derivatives (limited to those having a conjugated system in the polymer main chain) can be mentioned. The above-mentioned polymers may be used alone or in combination of two or more.

The polymer layer 120 may contain components other than the anion-adsorbing conductive polymer. Components other than anion-adsorbing conductive polymers include, for example, polymers other than anion-adsorbing conductive polymers, inorganic particles that may be included in the separator coating layer, and known conductive aids and binders that may be included in the positive electrode 110. , solid polymer electrolytes, and inorganic solid electrolytes.

The thickness of the polymer layer 120 is not particularly limited, but is preferably 100 nm or more and 50 μm or less, more preferably 500 nm or more and 10 μm or less, and still more preferably 1.0 μm or more and 5.0 μm or less. By having the thickness of the polymer layer within the above range, the balance between the energy density and capacity of the lithium secondary battery 100 and the cycle characteristics can be improved.

In the lithium secondary battery 100, the content of the anion-adsorbing conductive polymer is preferably 1% or more and 15% in terms of capacity ratio with respect to the total capacity of the positive electrode active material and the anion-adsorbing conductive polymer. or less, more preferably 5% or more and 10% or less. Note that each capacity of the positive electrode active material and the anion-adsorbing conductive polymer can be measured by a conventionally known method.

(Electrolyte)
In the lithium secondary battery 100, the electrolyte may be permeated into the separator 130, or may be enclosed in a sealed container together with a laminate of the positive electrode 110, the polymer layer 120, the separator 130, and the negative electrode 140. The electrolyte is a solution containing an electrolyte and a solvent and having ion conductivity, and acts as a conductive path for lithium ions. Therefore, the lithium secondary battery 100 has a further reduced internal resistance and further improved energy density, capacity, and cycle characteristics.

The electrolyte in the electrolytic solution may contain a lithium salt, but may also contain other salts, such as Na, K, Ca, and Mg salts. Examples of electrolyte anions include, but are not limited to, I ^- , Cl ^- , Br ^- , F ^- , ClO ₄ ^- , BF ₄ ^- , PF ₆ ^- , AsF ₆ ^- , SO ₃ CF ₃ ^- , N(SO _2F ) _2- ^, N _{( SO2CF3 ) 2-} ^, N ⁽ _{SO2CF3CF3 ) 2-} ^, B _{( O2C2H4 ) 2- , B} ( _O2C2H4 )F _2- ^, B( _OCOCF3 ) _4- ^, _NO3- , ^SO42- _, and ^the like. From the viewpoint of enhancing the interaction between the anion-adsorbing conductive polymer and anions, the anions of the electrolyte include ClO ₄ ^- , BF ₄ ^- , PF ₆ ^- , AsF ₆ ^- , and N(SO ₂ F) ₂ ^- . Preferably, BF ₄ ^- , PF ₆ ^- and N(SO ₂ F) ₂ ^- are more preferable.

Examples of the lithium salt include, but are not limited to, LiI, LiCl, LiBr, LiF _{, LiBF4 , LiPF6} , _LiAsF6 , LiSO3CF3 _, LiN _{( SO2F} ) ₂ , _LiN ( _{SO2CF3 ) 2} , LiN( _SO2CF3CF3 ) ₂ , LiB _{(O2C2H4)2, LiB(O2C2H4)F2, LiB(OCOCF3)4 , LiNO3 , and Li2SO4 . From the viewpoint of} further improving the energy density, capacity, and cycle characteristics of the _{lithium secondary battery 100, the lithium salt is preferably LiN(SO2F ) 2} . The above lithium salts may be used alone or in combination of two or more.

The solvent is not particularly limited, but examples thereof include dimethoxyethane, dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, acetonitrile, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethylene carbonate, propylene carbonate, chloroethylene carbonate, fluoroethylene carbonate, difluoroethylene carbonate, trifluoromethyl propylene carbonate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, nonafluorobutyl methyl ether, nonafluorobutyl ethyl ether, tetrafluoroethyl tetrafluoropropyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, trimethyl phosphate, and triethyl phosphate. The above solvents may be used alone or in combination of two or more.

The concentration of the electrolyte in the electrolytic solution is not particularly limited, but is preferably 0.5 M or more, more preferably 0.7 M or more, even more preferably 0.9 M or more, and even more preferably 1.1 M or more. By having the electrolyte concentration within the above range, the lithium secondary battery 100 can achieve both better cycle characteristics and higher energy density and capacity. The upper limit of the electrolyte concentration is not particularly limited, and the electrolyte concentration may be 10.0 M or less, 5.0 M or less, or 2.0 M or less.

(Use of lithium secondary batteries)
2 shows one mode of use of the lithium secondary battery of this embodiment. In the lithium secondary battery 200, a positive electrode terminal 220 and a negative electrode terminal 210 for connecting the lithium secondary battery to an external circuit are joined to the positive electrode current collector 150 and the negative electrode 140, respectively, in the lithium secondary battery 100. The lithium secondary battery 200 is charged and discharged by connecting the negative electrode terminal 210 to one end of the external circuit and the positive electrode terminal 220 to the other end of the external circuit.

The lithium secondary battery 200 is charged by applying a voltage between the positive terminal 220 and the negative terminal 210 such that a current flows from the negative terminal 210 through the external circuit to the positive terminal 220. By charging the lithium secondary battery 200, lithium metal is deposited on the negative electrode. When charging the lithium secondary battery 200, especially in the early stage of charging, the anion-adsorbing conductive polymer of the polymer layer 120 adsorbs anions in the electrolyte, resulting in lithium metal precipitation on the negative electrode. .

The lithium secondary battery 200 has a solid electrolyte interface layer (SEI layer) may be formed. The formed SEI layer is not particularly limited, but may include, for example, an inorganic compound containing lithium, an organic compound containing lithium, and the like. A typical average thickness of the SEI layer is 1 nm or more and 10 μm or less.

When the positive electrode terminal 220 and the negative electrode terminal 210 are connected to the lithium secondary battery 200 after charging, the lithium secondary battery 200 is discharged. As a result, lithium metal deposits formed on the negative electrode are electrolytically eluted. Furthermore, anions are released from the anion-adsorbing conductive polymer.

(Method of manufacturing lithium secondary battery)
The method for manufacturing the lithium secondary battery 100 as shown in FIG. 1 is not particularly limited as long as it is a method capable of manufacturing a lithium secondary battery having the above-mentioned configuration, and examples thereof include the following methods.

First, the positive electrode 110 is prepared by a known manufacturing method or by purchasing a commercially available product. The positive electrode 110 is manufactured, for example, as follows. The above-described positive electrode active material, a known conductive additive, and a known binder are mixed to obtain a positive electrode mixture. The compounding ratio is, for example, with respect to the entire positive electrode mixture, the positive electrode active material is 50% by mass or more and 99% by mass or less, the conductive additive is 0.5% by mass and 30% by mass or less, and the binder is 0.5% by mass. It may be less than % by mass. The obtained positive electrode mixture is applied onto one side of a metal foil (for example, Al foil) as a positive electrode current collector having a predetermined thickness (for example, 5 μm or more and 1 mm or less) and press-molded. The obtained molded body is punched out into a predetermined size by punching to obtain the positive electrode 110 formed on the positive electrode current collector 150.

Next, the above-mentioned negative electrode material, for example, a metal foil (for example, electrolytic Cu foil) with a size of 1 μm or more and 1 mm or less, is cleaned with a solvent containing sulfamic acid and then punched into a predetermined size, and then ultrasonically cleaned with ethanol. , a negative electrode 140 is obtained by drying.

Next, separator 130 having the above-described configuration is prepared. The separator 130 may be manufactured by a conventionally known method, or a commercially available one may be used.

The polymer layer 120 may be formed on one side of the separator 130 (the side facing the positive electrode 110), or may be formed on one side of the positive electrode 110 (the side facing the separator 130). The polymer layer 120 is formed by applying a solution obtained by dissolving the above-mentioned anion-adsorbing conductive polymer in a solvent such as m-cresol, water, or xylene to one side of the separator 130 or the positive electrode 110 using a dip coating method or a spin coating method. It can be obtained by applying by a method such as a coating method, followed by drying and removing the solvent. As a method for applying the polymer solution, a method using a device such as a comma coater, a gravure coater, or a die coater can also be used. Note that the solution containing the anion-adsorbing conductive polymer may contain polymers other than the anion-adsorbing conductive polymer, inorganic particles that may be included in the separator coating layer, and known conductive aids that may be included in the positive electrode 110. A binder, solid polymer electrolyte, inorganic solid electrolyte, etc. may be added.

The electrolytic solution may be prepared by dissolving the above electrolyte (typically, a lithium salt) in the above solvent.

The positive electrode current collector 150 on which the positive electrode 110 is formed, the separator 130, and the negative electrode 140 obtained as described above are laminated in this order to obtain a laminate as shown in FIG. 1. Note that, as described above, the polymer layer 120 is formed on one side of the separator 130 or the positive electrode 110. The lithium secondary battery 100 can be obtained by sealing the obtained laminate together with an electrolyte in a closed container. Examples of the closed container include, but are not limited to, a laminate film.

[Second embodiment]
(Lithium secondary battery)
FIG. 3 is a schematic cross-sectional view of a lithium secondary battery according to the second embodiment. As shown in FIG. 3, the lithium secondary battery 300 of the second embodiment includes a positive electrode current collector 150, a polymer layer 120 formed on the positive electrode current collector 150, and a polymer layer 120 formed on the positive electrode current collector 150. A positive electrode 110 disposed on the opposite side from the positive electrode current collector 150, a negative electrode 140 having no negative electrode active material, and a separator 130 disposed between the positive electrode 110 and the negative electrode 140, which are not shown in FIG. Equipped with an electrolyte that has not been used.

The configurations and preferred aspects of the electrolyte, positive electrode 110, polymer layer 120, separator 130, negative electrode 140, and positive electrode current collector 150 are similar to those of the lithium secondary battery 100 of the first embodiment, and the lithium secondary battery 300 has the same effects as the lithium secondary battery 100.

In the lithium secondary battery 300, since the positive electrode current collector 150 and the polymer layer 120 are in direct contact with each other, anion doping of the anion-adsorbing conductive polymer, that is, anion adsorption is more likely to occur, and the lithium secondary It is thought that the battery 300 has even better cycle characteristics than the lithium secondary battery 100.

The lithium secondary battery 300 can be manufactured in a similar manner to the manufacturing method of the lithium secondary battery 100 in the first embodiment, except that a polymer layer 120 is formed on one side of the positive electrode collector 150 in a manner similar to the method for forming the polymer layer 120 in the first embodiment, and a positive electrode 110 is formed on the side of the polymer layer 120 opposite the positive electrode collector 150 in a manner similar to the method for forming the positive electrode 110 in the first embodiment.

[Third embodiment]
(Lithium secondary battery)
Fig. 4 is a schematic cross-sectional view of a lithium secondary battery according to the third embodiment. As shown in Fig. 4, the lithium secondary battery 400 according to the third embodiment includes a positive electrode 410, a negative electrode 140 having no negative electrode active material, a separator 130 disposed between the positive electrode 410 and the negative electrode 140, and an electrolyte not shown in Fig. 4. The positive electrode current collector 150 is disposed on the opposite side of the positive electrode 410 from the surface facing the separator 130.

The configurations and preferred aspects of the electrolytic solution, separator 130, negative electrode 140, and positive electrode current collector 150 are the same as those of the lithium secondary battery 100 of the first embodiment.

In addition to the positive electrode active material, the positive electrode 410 contains an anion-adsorbing conductive polymer. That is, the positive electrode 410 is obtained by adding an anion-adsorbing conductive polymer to the positive electrode 110 in the lithium secondary battery 100 of the first embodiment. According to this embodiment, the lithium secondary battery 400 not only has the same effects as the lithium secondary battery 100, but also can be manufactured more easily and has excellent productivity. I can do it.

Types and examples of the positive electrode active material contained in the positive electrode 410 and components other than the positive electrode active material that may be contained in the positive electrode 410 (specifically, a conductive aid, a binder, a solid polymer electrolyte, and an inorganic solid electrolyte) , preferred embodiments, and content are the same as those of the positive electrode 110.

The definition, examples, and preferred embodiments of the anion-adsorbing conductive polymer contained in the positive electrode 410 are the same as those of the polymer layer 120 in the lithium secondary battery 100 of the first embodiment. In the positive electrode 410, the content of the anion-adsorbing conductive polymer is preferably 1% or more and 15% or less, more preferably 1% or more and 15% or less, based on the total capacity of the positive electrode active material and the anion-adsorbing conductive polymer. is adjusted to be 5% or more and 10% or less. The content of the anion adsorbing conductive polymer may be 1% by mass or more and 25% by mass or less, or 3% by mass or more and 20% by mass or less based on the entire positive electrode 410. , 5% by mass or more and 15% by mass or less.

The lithium secondary battery 400 can be manufactured in the same manner as the lithium secondary battery 100, except that an anion-adsorbing conductive polymer is added in addition to the positive electrode active material when the positive electrode 110 is formed, and that the polymer layer 120 is not formed. In the manufacturing method of the lithium secondary battery 400, the step of forming the polymer layer 120 can be omitted compared to the manufacturing method of the lithium secondary battery 100, so that the lithium secondary battery can be manufactured efficiently.

[Fourth embodiment]
(Lithium secondary battery)
Fig. 5 is a schematic cross-sectional view of a lithium secondary battery according to the fourth embodiment. As shown in Fig. 5, a lithium secondary battery 500 according to the fourth embodiment includes a positive electrode 110, a negative electrode 140 having no negative electrode active material, a solid electrolyte 510 disposed between the positive electrode 110 and the negative electrode 140, and a polymer layer 120 disposed between the positive electrode 110 and the solid electrolyte 510. A positive electrode current collector 150 is disposed on the opposite side of the positive electrode 110 from the surface facing the polymer layer 120.

The configurations of the positive electrode 110, the polymer layer 120, the negative electrode 140, and the positive electrode current collector 150, and their preferred aspects are the same as those of the lithium secondary battery 100 of the first embodiment, and the lithium secondary battery 500 has the following configurations: It has the same effect as the lithium secondary battery 100. The lithium secondary battery 500 may include an electrolyte like the lithium secondary battery 100 includes.

(solid electrolyte)
Generally, in a battery including a liquid electrolyte, the physical pressure applied from the electrolyte to the negative electrode surface tends to vary depending on the location due to fluctuations in the liquid. On the other hand, since the lithium secondary battery 500 includes the solid electrolyte 510, the pressure applied from the solid electrolyte 510 to the surface of the negative electrode 140 is uniform, and the shape of the lithium metal deposited on the surface of the negative electrode 140 can be made more uniform. can. That is, according to such an aspect, the lithium metal deposited on the surface of the negative electrode 140 is further suppressed from growing in a dendrite shape, so that the cycle characteristics of the lithium secondary battery 500 are further improved.

The solid electrolyte 510 is not particularly limited as long as it is generally used in lithium solid secondary batteries, but a known material can be appropriately selected depending on the application of the lithium secondary battery 500. The solid electrolyte 510 preferably has ionic conductivity and no electrical conductivity. By having the solid electrolyte 510 have ionic conductivity and no electrical conductivity, the internal resistance of the lithium secondary battery 500 is further reduced and short circuits inside the lithium secondary battery 500 can be further suppressed. As a result, the energy density, capacity, and cycle characteristics of the lithium secondary battery 500 are further improved.

The solid electrolyte 510 is not particularly limited, but includes, for example, one containing a resin and a lithium salt. Examples of such resins include, but are not limited to, resins having ethylene oxide units in their chains and/or side chains, acrylic resins, vinyl resins, ester resins, nylon resins, polysiloxanes, polyphosphazenes, and polyvinylidene fluoride. , polymethyl methacrylate, polyamide, polyimide, aramid, polylactic acid, polyethylene, polystyrene, polyurethane, polypropylene, polybutylene, polyacetal, polysulfone, and polytetrafluoroethylene. The above resins may be used alone or in combination of two or more.

The lithium salt contained in the solid electrolyte 510 is not particularly limited, but includes, for example, the salts listed as lithium salts that may be contained in the electrolyte of the lithium secondary battery 100. The above lithium salts may be used alone or in combination of two or more.

Generally, the content ratio of resin and lithium salt in a solid electrolyte is determined by the ratio of oxygen atoms in the resin to lithium atoms in the lithium salt ([Li]/[O]). In the solid electrolyte 510, the content ratio of resin and lithium salt is such that the above ratio ([Li]/[O]) is preferably 0.02 or more and 0.20 or less, more preferably 0.03 or more and 0.15. Hereinafter, it is further preferably adjusted to 0.04 or more and 0.12 or less.

The solid electrolyte 510 may contain components other than the resin and lithium salt. Such components include, but are not limited to, solvents and salts other than lithium salts. Examples of salts other than lithium salts include, but are not limited to, salts of Na, K, Ca, and Mg. Examples of solvents include, but are not limited to, those exemplified in the electrolyte that the lithium secondary battery 100 may contain. The above-mentioned solvents and salts other than lithium salts may be used alone or in combination of two or more.

The average thickness of the solid electrolyte 510 is preferably 20 μm or less, more preferably 18 μm or less, and even more preferably 15 μm or less. According to such an embodiment, the volume occupied by the solid electrolyte 510 in the lithium secondary battery 500 is reduced, so that the energy density of the lithium secondary battery 500 is further improved. In addition, the average thickness of the solid electrolyte 510 is preferably 5 μm or more, more preferably 7 μm or more, and even more preferably 10 μm or more. According to such an embodiment, the positive electrode 110 and the negative electrode 140 can be more reliably isolated, and the battery can be further prevented from being short-circuited.

Solid electrolyte 510 includes a gel electrolyte. The gel electrolyte is not particularly limited, but includes, for example, one containing a polymer, an organic solvent, and a lithium salt. Examples of the polymer in the gel electrolyte include, but are not limited to, copolymers of polyethylene and/or polyethylene oxide, polyvinylidene fluoride, and copolymers of polyvinylidene fluoride and hexafluoropropylene.

(Method for manufacturing secondary batteries)
The lithium secondary battery 500 can be manufactured in the same manner as the method for manufacturing the lithium secondary battery 100 according to the first embodiment described above, except that a solid electrolyte is used in place of the separator.

The method for producing the solid electrolyte 510 is not particularly limited as long as it can obtain the above-mentioned solid electrolyte 510, but may be, for example, as follows. A resin conventionally used in solid electrolytes and a lithium salt (for example, the resin and lithium salt described above as the solid electrolyte 510 may contain) are dissolved in an organic solvent (for example, N-methylpyrrolidone, acetonitrile). The obtained solution is cast onto a molding substrate to a predetermined thickness to obtain the solid electrolyte 510. Here, the compounding ratio of the resin and the lithium salt may be determined by the ratio ([Li]/[O]) of the oxygen atoms of the resin to the lithium atoms of the lithium salt, as described above. The ratio ([Li]/[O]) is, for example, 0.02 or more and 0.20 or less. The molding substrate is not particularly limited, but for example, a PET film or a glass substrate may be used.

[Modification]
The above-described embodiment is an example for explaining the present invention, and is not intended to limit the present invention to only this embodiment. The present invention can be modified in various ways without departing from the gist of the invention.

For example, in the lithium secondary battery 100 of the first embodiment, separators 130 may be formed on both sides of the negative electrode 140. In this case, in the lithium secondary battery, each structure is laminated in the following order: positive electrode current collector/positive electrode/polymer layer/separator/negative electrode/separator/polymer layer/positive electrode/positive electrode current collector. According to such an embodiment, the capacity of the lithium secondary battery can be further improved.

The lithium secondary battery 500 may be a lithium solid state secondary battery. According to such an aspect, since it is not necessary to use an electrolyte, the problem of electrolyte leakage does not occur, and the safety of the battery is further improved.

In a lithium secondary battery, the anion-adsorbing conductive polymer only needs to be included in a layer disposed between the positive electrode current collector and the separator, and the layer containing the anion-adsorbing conductive polymer is The present invention is not limited to the polymer layer and the positive electrode, and may take any form. Moreover, two polymer layers containing an anion-adsorbing conductive polymer may be separately arranged between the positive electrode current collector and the positive electrode and between the positive electrode and the separator.

In addition, in the lithium secondary battery 100 and the lithium secondary battery 300, the positive electrode 110 may contain an anion-adsorbing conductive polymer. That is, the lithium secondary battery may include a polymer layer containing an anion-adsorbing conductive polymer and a positive electrode containing an anion-adsorbing conductive polymer.

Furthermore, in the lithium secondary battery 500, the polymer layer 120 may be disposed between the positive electrode current collector 150 and the positive electrode 110, and the positive electrode 110 may include an anion-adsorbing conductive polymer.

When the anion-adsorbing conductive polymer is divided into two or more layers and contained in a lithium secondary battery, the total content of the anion-adsorbing conductive polymer is adjusted to be, in terms of volume ratio, preferably 1% or more and 15% or less, more preferably 5% or more and 10% or less, relative to the total capacity of the positive electrode active material and the anion-adsorbing conductive polymer.

Furthermore, in the lithium secondary battery, an auxiliary member may be disposed between the separator and the negative electrode to assist the precipitation and/or elution of lithium metal during charging and discharging. Such an auxiliary member may include a member containing a metal that alloys with lithium metal, and may be, for example, a metal layer formed on the surface of the negative electrode. Examples of such a metal layer include a layer containing at least one selected from the group consisting of Si, Sn, Zn, Bi, Ag, In, Pb, Sb, and Al. The average thickness of the metal layer may be, for example, 5 nm or more and 500 nm or less.

According to the aspect in which the lithium secondary battery 100 has the above-mentioned auxiliary member, the affinity between the negative electrode and the lithium metal deposited on the negative electrode is further improved, so that the lithium metal deposited on the negative electrode is further prevented from peeling off, and the cycle characteristics tend to be further improved. The auxiliary member may contain a metal that is alloyed with lithium metal, but its capacity is sufficiently smaller than the capacity of the positive electrode. In a typical lithium ion secondary battery, the capacity of the negative electrode active material of the negative electrode is set to be approximately the same as the capacity of the positive electrode, but the capacity of the auxiliary member is sufficiently smaller than the capacity of the positive electrode, so that the lithium secondary battery 100 having such an auxiliary member can be said to have a "negative electrode that does not have a negative electrode active material". Therefore, the capacity of the auxiliary member is sufficiently small compared to the capacity of the positive electrode, for example, 20% or less, 15% or less, 10% or less, or 5% or less.

The lithium secondary battery of this embodiment may or may not have a lithium foil formed between the separator or the solid electrolyte and the negative electrode before initial charging. In the lithium secondary battery of this embodiment, if lithium foil is not formed between the separator or solid electrolyte and the negative electrode before initial charging, highly flammable lithium metal may not be used during manufacturing. As a result, the lithium secondary battery has even better safety and productivity.

The lithium secondary battery of this embodiment may or may not have a current collector disposed on the surface of the negative electrode so as to be in contact with the negative electrode. Such a current collector is not particularly limited, but includes, for example, those that can be used as a negative electrode material. Note that when the lithium secondary battery does not have a negative electrode current collector, the negative electrode itself acts as a current collector.

In the lithium secondary battery of this embodiment, a terminal for connecting to an external circuit may be attached to the positive electrode current collector and/or the negative electrode. For example, a metal terminal (for example, Al, Ni, etc.) with a size of 10 μm or more and 1 mm or less may be bonded to one or both of the positive electrode current collector and the negative electrode, respectively. As a joining method, a conventionally known method may be used, for example, ultrasonic welding may be used.

In this specification, "high energy density" or "high energy density" means that the capacity per total volume or total mass of the battery is high, preferably 800Wh/L or more or 350Wh/L. /kg or more, more preferably 900Wh/L or more or 400Wh/kg or more, still more preferably 1000Wh/L or more or 450Wh/kg or more.

Furthermore, in this specification, "excellent cycle characteristics" means that the rate of decrease in battery capacity is low before and after the number of charge/discharge cycles that can be expected in normal use. In other words, when comparing the first discharge capacity after the initial charge and the discharge capacity after the expected number of charge/discharge cycles in normal use, the discharge capacity after the charge/discharge cycle is the same as the discharge capacity after the initial charge. This means that the discharge capacity has hardly decreased compared to the first discharge capacity. Here, "the number of times that can be expected in normal use" depends on the application in which the lithium secondary battery is used, but for example, 30 times, 50 times, 70 times, 100 times, 300 times, or 500 times. be. In addition, "the discharge capacity after a charge/discharge cycle has hardly decreased compared to the first discharge capacity after the initial charge" depends on the application in which the lithium secondary battery is used, but for example, The discharge capacity after the discharge cycle is 60% or more, 65% or more, 70% or more, 75% or more, 80% or more, or 85% or more of the first discharge capacity after the initial charge. means.

[Anode-free battery]
The anode-free battery of this embodiment includes a positive electrode current collector, a negative electrode, a separator disposed between the positive electrode current collector and the negative electrode, and a positive electrode active material disposed between the positive electrode current collector and the separator. and an electrolytic solution, and includes a layer containing an anion-adsorbing conductive polymer between the positive electrode current collector and the separator. In the anode-free battery of this embodiment, in the lithium secondary battery described above, the metal ions serving as charge carriers are not limited to lithium ions, but may also be sodium ions, calcium ions, magnesium ions, aluminum ions, etc. be.

The anode-free battery of this embodiment has the same configuration as the lithium secondary battery described above, except that the metal ions serving as charge carriers are not limited to lithium ions, and may be sodium ions, calcium ions, magnesium ions, aluminum ions, etc., and has the same effects as the lithium secondary battery described above. Therefore, the anode-free battery of this embodiment can provide an anode-free battery with high energy density and capacity and excellent cycle characteristics.

In addition, the negative electrode active material in an anode-free battery means a metal ion that becomes a charge carrier in a battery, or a material for holding the metal at the negative electrode, and may be referred to as a host material for the metal element (typically the metal). In addition, the positive electrode active material in an anode-free battery means a metal ion that becomes a charge carrier in a battery, or a material for holding the metal at the positive electrode, and may be referred to as a host material for the metal element (typically the metal ion). The negative electrode active material and positive electrode active material in an anode-free battery may be conventionally known materials.

Hereinafter, the present invention will be explained in more detail using Examples and Comparative Examples. The present invention is not limited in any way by the following examples.

[Example 1]
A lithium secondary battery was produced as follows.
First, a 10 μm electrolytic Cu foil was cleaned with a solvent containing sulfamic acid, then punched out into a predetermined size (45 mm x 45 mm), further ultrasonically cleaned with ethanol, and then dried. Thereafter, the Cu foil was degreased, washed with pure water, and then immersed in a plating bath containing Sb ions. By electrolytically plating the surface of the Cu foil while the Cu foil was left horizontally, Sb with a thickness of 100 nm was plated as a metal layer on the surface of the Cu foil. The Cu foil was taken out of the plating bath, washed with ethanol, and then washed with pure water. A Cu foil coated with an Sb thin film was used as the negative electrode.

A separator of a specified size (50 mm x 50 mm) and a thickness of 16 μm was prepared, consisting of a 12 μm polyethylene microporous membrane coated on both sides with 2 μm of polyvinylidene fluoride (PVdF).

Next, polyaniline, which is commercially available as a conductive polymer, was dissolved in m-xylene to obtain a polymer solution. The polymer solution containing polyaniline was applied to one side of the separator and dried to form a polymer layer made of polyaniline. The thickness of the polymer layer was 1.0 μm. The content of the anion-adsorbing conductive polymer was 8.0% by volume relative to the total volume of the positive electrode active material and the anion-adsorbing conductive polymer.

The positive electrode was prepared as follows. _{A mixture} of ₉₆ parts by mass of _{LiNi0.85Co0.12Al0.03O2} as a positive electrode active material, 2 parts by mass of carbon black as a conductive assistant, and 2 parts by mass of polyvinylidene fluoride (PVdF) as a binder was applied to one side of a 12 μm Al foil as a positive electrode current collector and press molded. The obtained molded body was punched out to a predetermined size (40 mm x 40 mm) by punching to obtain a positive electrode formed on the positive electrode current collector.

The electrolyte was prepared as follows: A 1.25 M LiFSI solution was prepared by dissolving LiN(SO ₂ F) ₂ (LiFSI) as an electrolyte in a solvent of a 10:90 volumetric ratio of dimethoxyethane (DME) and 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether (TFEE).

The positive electrode formed on the positive electrode current collector obtained as described above, the separator on which the polymer layer was formed, and the negative electrode were laminated in this order to obtain a laminate as shown in Figure 1. Furthermore, a 100 μm Al terminal and a 100 μm Ni terminal were joined to the positive electrode current collector and the negative electrode, respectively, by ultrasonic welding, and then inserted into a laminate exterior body. Next, the above-mentioned electrolyte was injected into the exterior body. The exterior body was sealed to obtain a lithium secondary battery.

[Examples 2 to 5]
A lithium secondary battery was obtained in the same manner as in Example 1, except that, in forming the polymer layer, each of the anion-adsorbing conductive polymers shown in Table 1 was used instead of polyaniline. Note that, each of the anion-adsorbing conductive polymers used was a commercially available product, and the thickness of the polymer layer was set to be the same as in Example 1.

[Examples 6 to 8]
A lithium secondary battery was obtained in the same manner as in Example 1, except that in producing the negative electrode, an Sb metal layer was not formed, and a 10 μm electrolytic Cu foil was used as the negative electrode, and in forming the polymer layer, each anion-adsorbing conductive polymer shown in Table 1 was used instead of polyaniline. Note that each anion-adsorbing conductive polymer used was a commercially available product, and the thickness of the polymer layer was set to be the same as in Example 1.

[Example 9]
A Cu foil coated with a thin Sb film was prepared as a negative electrode in the same manner as in Example 1. The same separator and electrolyte as in Example 1 were also prepared.

The positive electrode was produced as follows. 85 parts by mass of LiNi _0.85 Co _0.12 Al _0.03 O ₂ as a positive electrode active material, 2.0 parts by mass of carbon black as a conductive aid, 3.0 parts by mass of polyvinylidene fluoride (PVdF) as a binder, and anion adsorption property. A mixture of 10 parts by mass of polyaniline as a conductive polymer was coated on one side of a 12 μm Al foil as a positive electrode current collector, and press-molded. The obtained molded body was punched out into a predetermined size (40 mm x 40 mm) to obtain a positive electrode formed as a positive electrode current collector. The content of the anion-adsorptive conductive polymer was 8.0% in terms of capacity ratio with respect to the total capacity of the positive electrode active material and the anion-adsorptive conductive polymer.

The positive electrode, separator, and negative electrode formed on the positive electrode current collector obtained as described above were laminated in this order to obtain a laminate as shown in FIG. 4. A lithium secondary battery was obtained in the same manner as in Example 1 using the obtained laminate.

[Comparative Example 1]
A lithium secondary battery was obtained in the same manner as in Example 1, except that the polymer layer was not formed.

[Evaluation of energy density and cycle characteristics]
The energy density and cycle characteristics of the lithium secondary batteries produced in each example and comparative example were evaluated as follows.

The produced lithium secondary battery was charged at 7 mA until the voltage reached 4.2 V (initial charge), and then discharged at 7 mA until the voltage reached 3.0 V (hereinafter referred to as "initial discharge"). . Next, a cycle of charging at 35 mA until the voltage reached 4.2 V and discharging at 35 mA until the voltage reached 3.0 V was repeated in an environment at a temperature of 25°C. For each example, the capacity determined from the initial discharge (hereinafter referred to as "initial capacity") is shown in Table 1. Further, for each example, the number of cycles when the discharge capacity reached 80% of the initial capacity (referred to as "80% cycle number" in the table) is shown in Table 1.

In Table 1, "PAn" is polyaniline, "Ppy" is polypyrrole, "PTp" is polythiophene, "PEDOT" is polyethylenedioxythiophene, "PPP" is polyp-phenylene, and "PF" is polypropylene. fluorene, "PPv" means poly p-phenylene vinylene, "PTv" means polythienylene vinylene, "PE" means polyethylene microporous membrane, and NCA means LiNi _0.85 Co _0.12 Al _0.03 O ₂ . Further, "-" in the column of polymer layer means that there is no polymer layer.

From Table 1, it can be seen that Examples 1 to 9, which include a layer containing an anion-adsorbing conductive polymer between the positive electrode collector and the separator, have higher initial capacity and 80% cycle count, and are superior in capacity and cycle characteristics, compared to Comparative Example 1, which does not.

Since the lithium secondary battery of the present invention has high energy density and capacity and excellent cycle characteristics, it has industrial applicability as a power storage device used in various applications.

100,200,300,400,500... Lithium secondary battery, 110,410... Positive electrode, 120... Polymer layer, 130... Separator, 140... Negative electrode, 150... Positive electrode current collector, 210... Negative electrode terminal, 220... Positive electrode Terminal, 510...Solid electrolyte.

Claims (11)

a positive electrode current collector;
a negative electrode having no negative electrode active material;
a separator disposed between the positive electrode current collector and the negative electrode;
a positive electrode having a positive electrode active material disposed between the positive electrode current collector and the separator;
electrolyte and
A lithium secondary battery comprising:
a layer containing an anion-adsorbing conductive polymer between the positive electrode current collector and the separator;
Lithium secondary battery. A positive electrode current collector;
a negative electrode having no negative electrode active material;
a solid electrolyte disposed between the positive electrode current collector and the negative electrode;
a positive electrode having a positive electrode active material disposed between the positive electrode current collector and the solid electrolyte;
A lithium secondary battery comprising:
a layer containing an anion-adsorbing conductive polymer between the positive electrode current collector and the solid electrolyte;
Lithium secondary battery. The lithium secondary battery according to claim 1 or 2, wherein a polymer layer containing the anion-adsorbing conductive polymer is disposed between the positive electrode current collector and the positive electrode. The lithium secondary battery according to claim 1 or 2, wherein a polymer layer containing the anion-adsorbing conductive polymer is disposed on a surface of the positive electrode opposite to the positive electrode current collector. The lithium secondary battery according to any one of claims 1 to 4, wherein the positive electrode contains the anion-adsorbing conductive polymer. The content of the anion-adsorbing conductive polymer in the lithium secondary battery is 1% or more and 15% or less in terms of capacity ratio with respect to the total capacity of the positive electrode active material and the anion-adsorptive conductive polymer. The lithium secondary battery according to any one of claims 1 to 5. The lithium secondary battery is a lithium secondary battery in which charging and discharging are performed by depositing lithium metal on the surface of the negative electrode and electrolytically dissolving the deposited lithium. The lithium secondary battery according to item 1. The negative electrode is an electrode made of at least one member selected from the group consisting of Cu, Ni, Ti, Fe, and other metals that do not react with Li, alloys thereof, and stainless steel (SUS). The lithium secondary battery according to any one of claims 1 to 7. The lithium secondary battery according to claim 1, wherein no lithium foil is formed on the surface of the negative electrode before initial charging. The lithium secondary battery according to any one of claims 1 to 9, having an energy density of 350 Wh/kg or more. a positive electrode current collector;
a negative electrode;
a separator disposed between the positive electrode current collector and the negative electrode;
a positive electrode having a positive electrode active material disposed between the positive electrode current collector and the separator;
electrolyte and
An anode-free battery comprising:
a layer containing an anion-adsorbing conductive polymer between the positive electrode current collector and the separator;
Anode free battery.

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